Cut back the lateral branches to 12 inches in length for black raspberries and 18 inches for purple raspberries. Starting in late May or when the new growth reaches a height of 36 to 48 inches, pinch out or cut off the shoot tips.
Remove about 3 to 4 inches of the shoot bushfall.buzzted Reading Time: 5 mins. Jul 27, Black or Purple Raspberry Bush Pruning.
Remove fruiting canes after harvest. Tip prune new shoots in early spring 3 to 4 inches ( cm.) to encourage branching. Top these canes again 3 to 4 inches ( cm.) in summer. Then after harvest, remove all dead canes and those smaller than ½ inches (1 cm.) in diameter. Fall-bearing red raspberries can be pruned two different ways in March or early April.
One pruning option is to prune out all weak, diseased, and damaged canes at ground level. Leave the largest, most vigorous canes.
Cut back the tips of the canes that remain. Remove approximately the upper one-third of the canes. Black and Purple Raspberries. Remove the small, weak canes, leaving only four or five of the largest, most vigorous canes per clump or plant. Cut back the lateral (side) branches to 12 inches in length for black raspberries and 18 inches for purple raspberries. May 06, Raspberries of both summer and fall bearing varieties should be pruned in the winter.
This is because the berry canes are fully dormant during this time, so any pruning will stimulate growth, rather than damaging the current growth pattern. Raspberries can be pruned any time between November and March%(64).